This invention relates generally to digital integrated electronic circuits and more particularly to a digital dynamic multiplexer (MUX).
A multiplexer (or MUX, or data selector) has a group of control inputs that is used to select one of a group of data inputs and connect that input, or relay the value on that input, to the output terminal. MUX""s have been implemented in many different logic families including static logic families and dynamic logic families. One such implementation of a dynamic logic MUX is shown in FIG. 1.
Unfortunately, the dynamic logic MUX shown in FIG. 1 suffers from at least one problem. Subthreshold leakage current through transistors on the nonselected inputs can cause the output to switch incorrectly. This problem is aggravated when, to increase speed, the process technology is modified to make the threshold voltage of the transistors smaller.
A dynamic logic multiplexer has pullups on its input signals that pull-up the input signals when not selected. This reduces leakage current that may contribute to incorrect switching of the output. The output stage of the multiplexer includes a latched dynamic node followed by two gain stages, and an open-drain output.